1. Field of the Invention
The invention relates to an air conditioning system for motor vehicles, which contains a connection piece for a pressure switch/pressure sensor, said connection piece being suitable, after the removal of the pressure switch/pressure sensor, for evacuating and filling the air conditioning system, so that the two usually separate functions are combined in one connection piece. The invention relates, furthermore, to an adapter which makes it possible to connect an evacuating and filling unit to a currently customary connection piece for a pressure switch/pressure sensor. The currently customary additional arrangement of connection pieces for evacuating and filling the air conditioning system thereby becomes superfluous.
2. Background Art
Motor vehicles are normally driven by means of internal combustion engines. These internal combustion engines, in turn, are maintained at a specific temperature level by means of a cooling circuit. To heat the interior of a motor vehicle, the circulating coolant of this cooling circuit is used, as a rule, said coolant discharging the heat contained in it to the interior via a heat exchanger and a blower.
Air conditioning systems are increasingly used for cooling the interior of a motor vehicle. The state of the art is, as described in viewing Handbuch Kraftfahrzeugtechnik [Manual of Motor Vehicle Technology], 2nd Edition, April 2001, p. 5 ff., in this case to cause a refrigerant compressor to be driven mechanically by the internal combustion engine of a motor vehicle. The refrigerant is conveyed from the compressor through a condenser, which discharges the heat from the refrigerant, and an adder to the expansion valve. Here, the refrigerant compressed in the compressor expands and subsequently evaporates in the evaporator and thus extracts heat from the ambient air in a known way. As a rule, the evaporator is integrated into the heating housing, so that the blower and the air distribution can be utilized for the heating of the motor vehicle. The refrigerant is led from the evaporator back to the compressor, and the refrigerant circuit is thus closed.
Alternatively to the expansion valve, a small capillary tube is often used as a throttling member. This is substantially more cost-effective than an expansion valve, but said adder then has to be replaced by an approximately twice as large accumulator in the line from the evaporator back to the compressor.
The regulation of air conditioning systems having small capillary tubes is usually carried out via a suitable pressure-sensitive component, such as a pressure switch or pressure sensor, which is likewise arranged in the line between the evaporator and compressor. In this case, use is made of the fact that, in the case of the customary refrigerant 134a, there is a direct relation between pressure and temperature, so that the temperature can be concluded from the measured pressure. This pressure switch or pressure sensor is usually fastened to an air conditioning system line via a fastening thread by means of a correspondingly designed connection piece, the connection piece containing a spring-loaded one-way valve which is very similar in its construction to customary motor vehicle wheel valves. The connection piece itself is, as a rule, welded or soldered to an air conditioning system line.
Irrespective of the type of regulation of the air conditioning system, normally a further connection piece for connecting a pressure switch or pressure sensor to the high-pressure line between the compressor and the regulating unit is attached, both in systems with an expansion valve and with systems with a small capillary tube. This pressure switch or pressure sensor serves, in general, as a high-pressure safety element for switching off the compressor when pressures are too high and is employed for controlling a radiator fan.
To fill with refrigerant, service and/or filling connection pieces are attached to the refrigerant lines. These connection pieces, too, contain spring-loaded valves. Via these connection pieces, by means of standardized quick-action couplings, the evacuation and first filling of the air conditioning system are carried out or service work is dealt with during the lifetime of the motor vehicle. These connection pieces, too, are normally welded or soldered to the air conditioning system lines.
The conventional filling quantity for an air conditioning system of a motor vehicle is at the present time, according to Vieweg, approximately 600 to 900 g of R 134a. Reliable operation of the air conditioning system is ensured as long as approximately 70% of the original filling quantity is still located in the refrigerant circuit. One disadvantage of present-day air conditioning systems is that small quantities of refrigerant may escape through the hoses and sealing rings of the air conditioning system. It is therefore advantageous to keep the number of sealing points as low as possible.
Since each connection piece requires an additional soldering operation, a reduction in the number of connection pieces consequently means a marked reduction in the number of soldering operations, and, moreover, there is a slightly lower consumption of material. Furthermore, in this way, two valves can be dispensed with.